THIS INVENTION relates to the general field of nut-cracking devices or assemblies, usable to break or crack the shell of a shelled nut fruit so that the nut therein can be removed for consumption purposes, and it has particular but not exclusive reference to a manually operable device for the cracking open of macadamia fruits and similar shelled nuts fruits.
Many nut fruits such as macadamia and walnut have a relatively hard shell which must be broken or cracked for accessing the nut therein. The shell is so hard that a mechanical device is required to break or crack it. Nut-cracking devices have been in use for many years, and some have included arrangements where a lever is mounted for movement against one of a pair of juxtaposed jaw members, such as provided in Australian Patent No. 648744. The nut-cracking device disclosed therein does not always provide a satisfactory nut-cracking function, as a substantially large force is required to be applied on the lever to crack harder shells of nut fruits, such as macadamia nut fruits or Queensland nut fruits, or there is insufficient movement of the moving jaws to crack some kinds of nuts. The device also is unnecessarily complicated.
The present invention aims to provide a manually operable nut-cracking device which alleviates the problems of the prior art, is simple, cheap and effective and yet will prove durable and long lasting in use. The present invention also aims to provide improved function in order to allow an operator to use either hand, left or right, and to reduce the distance of travelling of the lever arm from its fully inoperative to its fully operative position whilst also maintaining the cracking action positively and desirably controlled. Other aims and advantages of the invention may hereinafter become apparent.
With the forgoing in view, my invention resides broadly in a manually operable nut-cracking device including:
a frame having wall means and a mounting base;
a fixed jaw member and a movable jaw member mounted to the wall means in opposed relationship to define between them a nut holding station, the movable jaw member being urged away from the fixed jaw member by biassing means;
a lever arm pivotally connected by its proximal end with a first pivot shaft to an upper part of the wall means such that its distal end forms an operating handle movable between a fully inoperative position whereat the jaws members are at their fullest extent away from one another and a fully operative position whereat the jaws members are at their fullest extent closer to one another; and
a wedge shape cam formed on the proximal end of the lever arm;
wherein the first pivot shaft being arranged adjacent to the movable jaw member and the cam being so shaped that when a force is applied to the handle to move the lever arm from its fully inoperative position to a partially operative position intermediate the fully inoperative and the fully operative positions, a relatively greater mechanical advantage is generated between the cam and the movable jaw member than correspondingly when the lever arm is moved from its intermediate position to its fully operative position, whereat the movable jaw member terminating short of the fixed jaw member by a predetermined distance.
The term xe2x80x9cmechanical advantagexe2x80x9d as used herein means the ratio of the force on the movable jaw member to a force applied to the handle of the lever arm.
Preferably, one or both jaw members have multi-toothed or serrated nut-engaging faces for holding a nut to be cracked, the multi-toothed or serrated faces being outwardly divergent in the nut-receiving station so that a nut can be wedged therein and held between the jaw members.
It is preferred that the wedge shaped cam has an upper portion and a lower portion, and said upper portion is arranged to be relatively closer to the first pivot shaft than said lower portion.
In a preferred form, the movable jaw member is pivotally mounted to the wall means, and has a top end and a lower end. The wedge shaped cam is arranged so that its upper portion engages with the top end of the movable jaw member between the fully inoperative and intermediate positions of the lever arm, and the lower portion of the cam engages with the movable jaw member intermediate its top end and its pivot, whereby it can be seen that a decreased mechanical advantage is traded for a larger relative movement when the lever arm is moved from the intermediate position to the fully operative position.
It is further preferred that said top end of the movable jaw member has a corner proximal to said pivot shaft and said upper portion engages with the proximal corner between the fully inoperative and intermediate positions of the lever arm.
It is also preferred that the travelling of the lever arm from the fully inoperative position to the fully operative position is arranged to extend through substantially ninety degrees.
Preferably the biassing means includes a spring or a resilient pad member arranged to cause the movable jaw member to be biassed in a direction away from the fixed jaw member. More preferably the spring or resilient pad member extends between the two jaw members at or adjacent to the mounting base so that it allows the movable jaw member to be forced to move in the direction of the fixed jaw member against the bias thereof, while additionally the spring or resilient pad member may co-operate with the jaw members to define a base support of the nut-holding station.
The wall means of the frame may have opposed upstanding walls defining a channel therebetween, and the movable and fixed jaw members being arranged in the channel. Each of said walls may have a first wall portion and a second wall portion with a divergent gap therebetween. The fixed jaw member is fixedly secured to said first wall portions and the movable jaw member is pivotally secured to said second wall portions. Preferably, the movable jaw member is pivotally secured to said second wall portions with a second pivot shaft arranged adjacent to the base.
The base may be fixed to a tray so that nuts from the cracked nut fruits can be moved from the nut holding station into the tray. Preferably, the base is fixed to a medial position of the tray so that the device can be operated by left or right handed person.
Feet members or anti-slip buffers may be arranged to support the tray on a surface.